I know these male betta are being sold but do does anyone know if they have female half moon king Betta?

How many fry would there be?
What species can mate with male half moon king?
Is 10 gallons to small for 1 half moon king betta? What about 20 gallons?
Breeding any different then other species of betta?
Are micro worms the best culture for betta fry to eat?
I have done months of research but any information is more then welcome.
* I haven't bought the tanks or culture or betta yet at all

There are no "species" specification between the common bettas :) tail types, yes (unless you delve into the wild bettas, some are different in how they breed)

Fry numbers vary always. I got 233 fry. Next time I may only get 80. 45. 150. Etc

Best to ask the store if they sell female HM giants

10 gallons is fine for a giant. They produce more waste than the regular bettas, and in turn cannot be smushed into a 2 gallon for example.

Breeding is not different other than I hear they are more aggressive. But mine seems pretty laid back for a giant.

Microworms is fine, though baby brine shrimp is another great food source. If you successfully breed giants you will definitely need 2+ different live foods just to keep them fed.

If you cannot find a female HM giant, go with trying to find a half giant, a regular giant of another tail type (plakat perhaps). Otherwise a very large plakat girl may suffice if he is still small enough. Mine is only 3 inches since he is fairly new.